1. Field of the Invention
The present invention relates to a print apparatus and a print method that rotate a disc-like recording medium, such as a CD-R (Compact Disc-Recordable) or a DVD-RW (Digital Versatile Disc-Rewritable), a semiconductor storage medium, or other printed object and print visible information such as characters and designs by ejecting ink droplets onto a label surface or other print surface of the rotating printed object, and also relates to a recording medium driving apparatus that rotates a recording medium as one example of a printed object.
2. Description of the Related Art
One example of this type of print apparatus is disclosed by Japanese Unexamined Patent Application Publication No. H09-265760. Japanese Unexamined Patent Application Publication No. H09-265760 relates to an optical disc apparatus that is capable of printing on a removable optical disc. The optical disc apparatus disclosed in Japanese Unexamined Patent Application Publication No. H09-265760 is characterized by being an information storage apparatus that can carry out at least one of the recording and the reproduction of information using a removable optical disc and includes: a print head that prints on the optical disc; a print head driver that moves the print head in the radial direction of the optical disc; a spindle motor that rotates the optical disc; and a control unit that controls the print head, the print head driver, and the spindle motor, where the control unit causes the print head to scan across the optical disc to print on the optical disc.
The optical disc apparatus including disclosed in Japanese Unexamined Patent Application Publication No. H09-265760 demonstrates such an effect of printing a label on an optical disc without having to separately provide a dedicated label printer and with the disc still inserted in the optical disc apparatus (see Paragraph [0059]).
Another example of this type of print apparatus is disclosed by Japanese Unexamined Patent Application Publication No. 2004-110994. Japanese Unexamined Patent Application Publication No. 2004-110994 relates to an optical disc information recorder with ink jet printing apparatus. The optical disc information recorder with ink jet printing apparatus disclosed by Japanese Unexamined Patent Application Publication No. 2004-110994 is characterized by including: a head capable of reproducing and recording information that can be optically read on a recordable optical disc; and an ink jet print head that can print characters, designs, and the like on the label surface of the optical disc, where the characters, designs, and the like are printed on the label surface simultaneously with the recording of optical information on the optical disc.
The optical disc information recorder with ink jet printing apparatus disclosed by Japanese Unexamined Patent Application Publication No. 2004-110994 with the construction described above demonstrates such an effect of being able to record optical information on a recordable optical disc and simultaneously print on the label surface, which may not only greatly reduce the time required compared to when both processes are carried out separately in the related art apparatuses but may also use a compact construction where separate apparatuses do not need to be provided (see Paragraph [0050]).
However, both the optical disc apparatus disclosed by Japanese Unexamined Patent Application Publication No. H09-265760 and the optical disc information recorder with ink jet printing apparatus disclosed by Japanese Unexamined Patent Application Publication No. 2004-110994 are constructed so as to print visible information on the label surface of an optical disc by ejecting ink droplets onto the optical disc as it rotates from ejection nozzles provided on a print head. In apparatuses employing such construction, when the printing is carried out with the optical disc rotating at a constant angular velocity and with the ink droplets being ejected by the print head at a constant timing, there will be a difference in print density between the inner and outer peripheries of the print region.
FIG. 1A shows a state where ink droplets 103 ejected from a print head 102 have dripped onto a label surface 101a of the optical disc 101 such as a CD-R as one specific example of a printed object. As shown in FIG. 1A, in this example, the print head 102 includes sixteen ejection nozzles aligned in the radial direction of the optical disc 101, and when the ink droplets 103 are ejected from the ejection nozzles, a total of sixteen ink droplets 103 are dripped onto the label surface 101a. FIG. 1B shows a printed object that has been printed with the print head 102 ejecting the ink droplets 103 at a constant timing and with the optical disc 101 rotating at a constant angular velocity.
As shown in FIG. 1B, when printing is carried out with a constant angular velocity of the optical disc 101 and with the ink droplets 103 being ejected at a constant timing, the intervals between ink droplets 103 that are adjacent in the direction of rotation of the optical disc 101 (hereinafter “ink droplet intervals”) will differ between the inner and outer peripheries of the print region. That is, since the ink droplet intervals are proportionate to the distance (i.e., “radius”) from the center of rotation O of the optical disc 101, the ink droplet intervals in the inner periphery of the print region are narrower than the ink droplet intervals in the outer periphery. This implies that the amount of ink per unit area is greater in the inner periphery of the print region than in the outer periphery (i.e., the print density is higher), resulting in a difference in print density between the inner and outer peripheries of the print region.
To counteract such difference in print density between the inner and outer peripheries of the print region, Japanese Unexamined Patent Application Publication No. H09-265760 discloses one example that carries out control to make the rotational velocity of the optical disc relative to the print head, that is, the linear velocity, constant. Such control to make the linear velocity constant is effective when the print head is equipped with a single ejection nozzle. However, a plurality of ejection nozzles are provided on a typical print head so as to be aligned in the radial direction of the optical disc (or print region). Since the ink droplet interval differs according to the distance (i.e., “radius”) from the center of rotation of the optical disc to the respective ejection nozzles, there is the risk of a difference being produced in the print density.